Mobile Application for learning English language - suggestions please

Hello my friends, we are now finishing LingLing - mobile application for learning languages for iOS and Windows Phone.

It uses spaced repetition alghoritm (application similar to the classic system of supermemo), gamification and mnemonics.

I was using this application to learn Thai for about a year - 20-30 minutes a day learn gave me ability to read Thai and memorize 4000 new words a day (in the end of the year I plan to make 7000, which should already allow me to speak freely in this language).

Currently, we have free versions on Android:

The application for learning English LingLing:http://play.google.com/store/apps/details?id=com.hepilabs.lingling.englishThe application for learning Spanish LingLing:http://play.google.com/store/apps/details?id=com.hepilabs.lingling.spanishThe application for learning French LingLing:http://play.google.com/store/apps/details?id=com.hepilabs.lingling.frenchThe application for learning German LingLing:http://play.google.com/store/apps/details?id=com.hepilabs.lingling.germanThe application for learning Chinese LingLing:http://play.google.com/store/apps/details?id=com.hepilabs.lingling.chineseThe application for learning Thai LingLing:http://play.google.com/store/apps/details?id=com.hepilabs.lingling.thai

As we are now in the last stage of developing this app for iOS and Windows Phone i would like to ask you, if you could give me some feedback about the app - what we can improve, change or maybe you have some interesting ideas, how to make this app even more effective and easy to use.

If you have any problems with using the app - you can fin tutorial here http://www.joinlingling.com/ - here are all the features explained in details.